WASHINGTON — In an extraordinary public accusation, the head of the Senate Intelligence Committee declared on Tuesday that the CIA interfered with and then tried to intimidate a congressional investigation into the agency’s possible use of torture in terror probes during the Bush administration.

The CIA clandestinely removed documents and searched a computer network set up for lawmakers, said Sen. Dianne Feinstein in a long and biting speech on the Senate floor. In an escalating dispute with an agency she has long supported, she said the CIA may well have violated criminal laws and the U.S. Constitution.

At odds on major contentions, both sides noted the matter has now been handed to the Justice Department for further investigation and potential prosecution. The CIA’s inspector general, David Buckley, first referred the matter to Justice, and the CIA’s acting counsel responded by filing a criminal report about the intelligence committee staff.

“I am not taking it lightly,” Feinstein said of the tit-for-tat investigations. “I view the acting counsel general’s referral as a potential effort to intimidate this staff” in the interrogation investigation.

The dispute between the CIA and senators, which has been going on privately for more than five years, exploded into a public clash as the California Democrat offered a detailed account of the Senate’s secretive dealings with the CIA in an investigation of post-Sept. 11 interrogation and detention practices.

More broadly, all U.S. spy agencies have drawn intense scrutiny since revelations last summer about surveillance of Americans by the National Security Agency. The Obama administration has struggled to rebuild public trust since former analyst Edward Snowden made the disclosures. Feinstein has been one of the intelligence community’s most ardent advocates, arguing that the wide surveillance of people’s electronic and telephone communications was a necessary counterterrorism tool.

In the current matter, a long-running dispute has centered on whether waterboarding, a technique that simulates drowning, and other harsh interrogation techniques were factors in aiding the CIA’s antiterror efforts and helped the agency track down Osama bin Laden.

CIA Director John Brennan rejected Feinstein’s accusations, insisting that the agency was not trying to thwart the committee’s work and denying that it had been spying on the panel or the Senate. He said the appropriate authorities would look at the matter further and “I defer to them to determine whether or not there was any violation of law or principle.”

Brennan said if he did “something wrong, I would go to the president and he would be the one to ask me to stay or go.”

Brennan told Feinstein in a letter in January that he took responsibility for ordering CIA technicians to audit the computer systems used by the Senate staffers — to determine if there was a security breach.

In the letter, shared with CIA workers and obtained by The Associated Press on Tuesday, Brennan said he asked for the review after finding that Senate investigators may have “improperly obtained and/or retained … sensitive CIA documents” that the CIA had no record of sharing with them. He repeated his request for their return.

Feinstein insisted that her staff members acted appropriately in following an agreement worked out between her committee and then-CIA Director Leon Panetta in 2009.

But Feinstein and the CIA also have accused each other’s staffs of improper behavior. She said she had “grave concerns that the CIA’s search may well have violated the separation of powers principles embodied in the United States Constitution,” as well as the Fourth Amendment that prohibits unreasonable searches and seizures.

She said she has sought an explanation and an apology from the CIA. Neither has been forthcoming.

Feinstein received a standing ovation from her Democratic colleagues at a closed-party lunch on Tuesday. Several Republicans also expressed their concerns, but the Intelligence Committee’s top Republican, Saxby Chambliss of Georgia, wasn’t one of them.

He indicated he disagreed with her on the dispute, without providing specifics. He called for a study “on what happened so people can find out what the facts are.”

“We’re going to continue to deal with this internally,” he told reporters.

Other senators said the dispute had a chilling effect on congressional oversight.

“Heads should roll, people should go to jail if it’s true,” said Sen. Lindsey Graham, R-S.C. “If it is, the legislative branch should declare war on the CIA.”

Sen. Ron Wyden, D-Ore., an outspoken critic of the NSA practices, shared Feinstein’s concerns that laws were violated in an “unprecedented invasion by the CIA into computers used by Senate” investigators, and said misleading statements from intelligence leaders undermine their credibility.

It all goes back to 2009, when the CIA provided computers to congressional staffers in a secure room at a CIA facility in northern Virginia so the panel could review millions of pages of top secret documents in the course of its investigation of the agency’s detention and interrogation practices.

After first turning in 6.2 million pages without any index or search function — what Feinstein called “a true document dump” — the CIA provided an electronic search tool and congressional staff could make copies on their computers. The committee discovered that about 870 documents or pages of documents that they had been able to access had been removed in February 2010, and roughly another 50 were removed in mid-May 2010.

The removal of the documents “was the exact sort of CIA interference in our investigation that we sought to avoid at the outset,” she said.

A CIA official apologized for the removal of the documents on May 17, 2010.

Separately, committee staff had found draft versions of documents that Feinstein referred to as the “internal Panetta review.” Feinstein said those documents were written by CIA personnel to summarize and analyze the materials that had been provided to the committee. She said the internal documents were unique for their “analysis and acknowledgment of significant CIA wrongdoing.”

Those documents disappeared as well.

Jeremy Bash, former chief of staff for Panetta, said the director had asked CIA employees to draw up “concise summaries” of the documents made available to the Senate panel. Bash said neither Panetta nor any of his senior staff — including Bash — saw those summaries. To Bash’s knowledge, the summaries “did not say or analyze what was being provided to the committee or ask the (CIA employees) to come to conclusions,” he said. “Whether some people went beyond that … I don’t know.”

Then, on Jan. 15 of this year, Brennan informed Feinstein and Chambliss that the CIA had searched the computer network. Feinstein said that search also encompassed the committee’s network drive with its own internal work product and communications.

Feinstein did not name the CIA counsel who filed the criminal complaint, but two congressional officials identified the official as Robert Eatinger, who was involved in legal decisions involving agency interrogations during the Bush administration.

The officials commented only on condition of anonymity, citing the classified nature of the internal investigations.

Feinstein said the lawyer was the chief lawyer for the CIA’s Detention and Interrogation program from mid-2004 until it was terminated by an executive order signed by President Barack Obama in January 2009.

Feinstein said the lawyer “was mentioned by name more than 1,600 times in our study. And now this individual is sending a crimes report to the Department of Justice on the actions of congressional staff.” She added that the Senate report “details how CIA officers including the acting general counsel himself provided inaccurate information to the Department of Justice about the program.”

Brennan, who was questioned at an unrelated speech at the Council on Foreign Relations, said, “We are not in any way, shape or form trying to thwart this report.”

“I am confident that the authorities will deal with this appropriately,” he said. “I would just encourage some members of the Senate to take their time, to make sure they don’t overstate what they claim and what they apparently believe to be the truth.”

Democrats on the Senate Intelligence Committee completed their 6,300-page interrogation report last year and are revising it with CIA comments. Feinstein said she would ask the White House to declassify its 300-plus-page executive summary, and its conclusions.

When the report was first approved by Democrats on the committee in December 2012, Feinstein said her staffers came to the conclusion that the detention and interrogation program yielded little or no significant intelligence.

Noting that Obama has long opposed the CIA’s use of torture, spokesman Jay Carney said the White House strongly supports the Senate panel’s investigation, and that Obama wants the report’s findings to be eventually declassified. Feinstein, too, called for public release of the Senate report.